Group III-V photovoltaic devices have demonstrated high solar conversion efficiencies. (See, e.g., M. A. Green et al., “Solar Cell Efficiency Tables (version 49),” Prog. Photovolt. Res. Appl., vol. 25, no. 1, pp. 3-13, January 2017.) However, their widespread use is significantly limited due to the considerable expense of fabrication methods (typically metalorganic vapor phase epitaxy) and materials. Various strategies have been applied to lower the cost of these devices, including designing ultrathin solar cells modified with nanostructures (S.-M. Lee et al., “High Performance Ultrathin GaAs Solar Cells Enabled with Heterogeneously Integrated Dielectric Periodic Nanostructures,” ACS Nano, vol. 9, no. 10, pp. 10356-10365, October 2015), epitaxial lift-off (ELO) techniques to recycle substrates (C.-W. Cheng, K.-T. Shiu, N. Li, S.-J. Han, L. Shi, and D. K. Sadana, “Epitaxial Lift-off Process for Gallium Arsenide Substrate Reuse and Flexible Electronics,” Nat. Commun., vol. 4, p. ncomms2583, March 2013), and smarter light management. However, any advantages afforded by these strategies have a limited effect in the mass production of group III-V photovoltaics since the underlying epitaxial method exhibits a low growth rate.
Hydride vapor phase epitaxy (HVPE) is a growth technique offering a higher growth rate and less expensive reactants. However, this advantage has not translated into the practical use of HVPE to produce group III-V photovoltaics due to a number of technical challenges. These challenges are based upon the fact that HVPE is a near-to-equilibrium growth process, which makes the growth of individual layers, and thus the quality of the interfaces between adjacent material layers, very difficult to control.